1. Field of the Invention
The invention relates to a fuel supply system for a combustion chamber with premixing combustion in which a gaseous and/or liquid fuel is introduced as a secondary flow into a gaseous, ducted main flow, the secondary flow having a substantially smaller mass flow than the main flow and the premixing duct through which flow takes place having curved walls.
2. Discussion of Background
The mixing of fuel into a combustion air flow occurring in a premixing duct takes place, as a rule, by means of the radial introduction of the fuel into the duct by means of cross-jet mixers. The momentum of the fuel, however, is so small that almost complete mixing has only taken place after a distance of approximately 100 duct heights. Venturi mixers are also used. The introduction of fuel via grid arrangements is also known. Finally, the introduction of fuel before special swirlers is also used.
The appliances operating on the basis of cross jets or layer flows either have, as a result, very long mixing lengths or demand high injection momentums. In the case of premixing at high pressure and substoichiometric mixing conditions, the danger exists of flash-back of the flame or even self-ignition of the mixture. Flow separations and dead water zones in the premixing tube, thick boundary layers on the walls or possibly extreme velocity profiles over the cross section through which flow takes place can be the cause for self-ignition in the pipe or form paths by means of which the flame can flash back into the premixing tube from the combustion zone located downstream. It is therefore necessary to pay maximum attention to the geometry of the premixing length.